1. Field of the Invention
The present invention relates to a graphene composite nanofiber, and particularly, to a graphene composite nanofiber including monolayer graphenes and multilayer graphenes having a thickness of 10 nm or less, and having a nanoscale fibrous shape, and a preparation method thereof.
2. Background of the Invention
Graphene is a monolayer of graphite, and is a sheet of carbon atoms bound together with double electron bonds (called as an sp2 bond) in a thin film only one atom thick. Atoms in graphene are arranged in a honeycomb-style lattice pattern. This graphene is a very thin single flat sheet having a thickness of about 0.3 nm, and is a two-dimensional (2D) material for carbon. This graphene was firstly discovered by Andre Geim and Kostya Novoselov at Manchester University in England in 2004 (Novoselov, K. S. et al., Science, 2004, 306, 666-669). According to the American Physical Society (APS) and the English Nature Nanotechnology, this graphene is being spotlighted as one of the most remarkable new materials which can change the future information technology.
Differently from other carbon allotropes (e.g., carbon nanotube, graphite), the graphene is a semiconductor material having an energy gap of ‘0’. The graphene has characteristics such as high electron mobility, a quantum-hole characteristic (electrons inside graphenes behave like relativistic particles having no rest mass, with a speed of about 1,000,000 m/s), a low specific resistance, high to mechanical strength, and a wire surface area. Furthermore, the graphene is much more advantageous than carbon nanotubes due to low costs in an economic aspect.
However, in the aspect of application fields, the graphenes have a difficulty in being processed and treated like other carbon allotropes. Each layer of graphite (i.e., each graphene layer) is stacked to each other due to Van der Waal's force (5.9 kJ/mol carbon), thereby not implementing a physical property of a graphene monolayer. Since the first discovery of the graphenes, research has been mainly executed with respect to a method for preparing graphenes from graphite and dispersing the graphenes (Novoselov, K. S. et al., Science 2004, 306, 666-669), an analysis of various characteristics of graphenes (Kern, K. et al., Nano Lett. 2007, 7, 3499-3503), a method for preparing a graphene composite material (Stankovich, S. et al., Nature 2006, 442, 282-286), application fields to a transistor or a sensor (Vandersypen, K. et al., Nature Mater. 2008, 7, 151-157). Among the above research, the research about a graphene composite material has been actively executed based on suspension and dispersion of a graphene monolayer into a polymer matrix. And, research about a method for forming a graphene composite having a nanoscale one-dimensional structure has never been executed.